retrieve values mysqli_fetch - php

Question

I'm trying to get the id value from a table called usuario in the database, passing $username as parameter, the function $conexion->connect() returns a mysqli object. The functions give me no errors but it doesn't return the value from database. Am I missing something? or making any mistake.
Thanks for help.
public function checkUserNameExists($username){
$conexion = new Connection();
$conexion->connect();
$query = "select id from usuario where username = ?";
$reg = 0;
$stmt= $conexion->connect()->prepare($query);
$stmt->bind_param('s',$username);
$stmt->execute();
$stmt->bind_result($id);
while($stmt->fetch()){
$reg = $id;
}
$stmt->close();
return $reg;
}
This is the function connect() what is located in a class file "Connection"
public function connect(){
$mysqli = new mysqli($this->db_host,$this->db_user,$this->db_pass,$this->db_name);
if (mysqli_connect_errno()) {
printf("Connect failed: %s\n", mysqli_connect_error());
exit();
}
return $mysqli
}

Answer 1

public function checkUserNameExists($username){
$conexion = new Connection();
$conn = $conexion->connect();
$query = "select id from usuario where username = ?";
$reg = 0;
$stmt= $conn->prepare($query);
$stmt->bind_param('s',$username);
$stmt->execute();
$stmt->bind_result($id);
while($stmt->fetch()){
$reg = $id;
}
$stmt->close();
return $reg;
}
You should store the return value of new mysqli in a variable, and then use that variable to make queries or prepares from.